A Couple of Notes about NOAA’s RTG (Real-Time Global) Sea Surface Temperature Data

Recently, Robert Grumbine of NOAA (who I believe blogs at MoreGrumbineScience) was kind enough to stop by ClimateObservations to note an error I had made in a comment back in October at WattsUpWithThat.   See my October 13, 2014 at 1:06am reply to blogger James Abbott.  In that comment, I called the NOAA RTG (Real-Time Global) sea surface temperature data a reanalysis.  That was an error on my part. The NOAA RTG SST data are not a reanalysis.

Here’s Robert Grumbine’s comment (my boldface):

Bob, ran across an old comment of yours, saying that the NCEP RTG-High resolution SST analysis was a reanalysis. (http://wattsupwiththat.com/2014/10/12/september-2014-global-surface-landocean-and-lower-troposphere-temperature-anomaly-update/ down in the comments).

This is not correct. The RTG is an analysis, actually pretty similar in procedure to the Reynolds OIv2 quarter degree that you mention/use. The main difference is not analysis versus reanalysis, but that the RTG’s purpose is to produce the best current estimate of SST for use by weather prediction, while the OIv2 is aimed towards climate purposes.

Based on the NOAA NCEP webpage here, a fundamental difference between the NOAA RTG SST and Reynolds OI.v2 SST data is time resolution.  The time resolution of the daily RTG SST data is 1 day, while the time resolution of the daily Reynolds OI.v2 data is approximately 7 days.  (It appears as though the daily Reynolds OI.v2 data are smoothed/filtered over time, which would not be helpful for weather models.)

The supporting paper for the RTG SST data is Thiébaux et al. (2003) A New High-Resolution Blended Real-Time Global Sea Surface Temperature Analysis.  The full paper is available through that link.

The following map of global sea surface temperature anomalies based on the NOAA RTG data is available from the NOAA Real-time, global, sea surface temperature (RTG_SST_HR) analysis webpage.  Note the color-coding and 0.25 deg C contour levels. Also note that the NOAA RTG SST anomaly data are referenced to the base period of 1961-1990.


Sample Daily NOAA RTG SSTa Map

On the other hand, for the previous day, we have the next map, which is also from NOAA and it is presenting the Reynolds OI.v2 data. It is from their PSD Map Room Climate Products – Sea Surface Temperature (SST) webpage.  The contour levels are at 0.5 deg C and the base years for anomalies are 1971-2000.


Sample Daily NOAA Reynolds OI.v2 SSTa Map

From the same webpage, NOAA shifts the base years to the WMO-preferred 1981-2010 for their weekly, monthly and seasonal maps. The monthly map is shown below.  I present the monthly Reynolds OI.v2 data in my monthly sea surface temperature anomaly updates.


Sample Monthly NOAA Reynolds OI.v2 SSTa Map

The NOAA RTG SST and Reynolds OI.v2 SST data by definition are very similar datasets. They are comprised of in situ data from buoys and ship inlets and from satellites. The biggest real difference appears to be time resolution.

But NOAA’s presentations of the two datasets in maps are very different.

It’s blatantly obvious why alarmists prefer the maps of the NOAA RTG sea surface temperature anomaly data and how they intentionally fool themselves with illustrations that appear warm because of the scaling and outdated base years for anomalies.

About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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2 Responses to A Couple of Notes about NOAA’s RTG (Real-Time Global) Sea Surface Temperature Data

  1. Thanks, Bob.
    I had found the Real-time, global, sea surface temperature site and did not know that the anomaly data were referenced to of 1961-1990. Having used the Reynolds OI.v2 graphics, I was puzzled.
    Good article.

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